Implement `Service.fromServiceName`

[rassie]

Description of the feature or enhancement:

More often than not, there is a need to re-use an existing Service not created or managed by cdk8s. Elsewhere, you can re-use an existing ServiceAccount by calling ServiceAccount.fromServiceAccountName, but that functionality is not available for Services.

• 👋 I may be able to implement this feature request
• ⚠️ This feature might incur a breaking change

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This is a 🚀 Feature Request

[rassie]

This wasn't supposed to get closed.